Flow control of fuel



Nov. 16, 1943. c. E. MASON ET AL FLOW CONTROL F FUEL 2 SheetQ-Sheet 1Filed Sept. 14, 1939 INVENTOR CLlssso/v E. MASON. BY RALPH ,4. ROCKWELL.

1943- c. E. MASON ET AL FLOW CONTROL OF FUEL F iled Sept. 14, 1959 2Sheets-Sheet 2 I INVENTOR CLfJSO/V E. M450. 6 BY R01 4.1QOCAWELL.

fin. Guills *u i d ATToRNEks Patented Nov. 16, 1943 2,334,679 nowCONTROL OF FUEL Clesson E. Mason; Fo xboro, Mass and Ralph A.

Rockwell, Cranford, N. 1., assignors to The Foxboro Company, Foxboro,Mass, a corporation of Massachusetts I Application September 14, 1939,Serial 294,991

(o1. Isa-36,3)

11 Claims.

This invention relates to oil burning systems utilizing mechanicalatomizers for atomizing fuel oil burned and more particularly to amethod and apparatus for varying the rate of fuel consumption whilemaintaining efllcient atomization. The various types of burners used inthe oil firing art may be roughly classifiedin two groups. In one typeof burner the heavy fuel oil used for firing industrial equipment suchas furnaces, boilers, and the like, is dispersed or atomized by mixing apressure fluid such as steam with the mass of cit and forcing themixture of steam and oil through a nozzle to form a finespray. In

. which causes the oil when forcedfrom the chamber through the dischargenozzle to form a fine conical spray. The combustion efiiciency of theturner depends in largemeasure on the degree of atomization produced andhence it is desirable ing the oil to the burner tip chamber against themaximum static pressure in the burner tip chamber. A valve is providedin the return line and as the valve is opened it permits part of the oilsupplied to the burner to leave the burner through the return line andthus reduces the static pressure in the burner tip chamber. This systemhas the disadvantage that as the valve in the return line is opened andthe pressure in the chamber is reduced the flow through the tangentialpassages of the burner increases, although the outputofthe burner hasbeen decreased by opening the valve. This increased flow changes thecharacteristic of the spray.

Aside from this disadvantage such a system of varying the oil burneroutput has other inherent limitations and disadvantages in operationwhich militate against its use with automatic control apparatus tosatisfactorily correlate rate of oil burning with the behavior of thetemperature being controlled.

Another attempt to satisfy the problem of maintaining the desiredwhirling motion of the oil in the burner tip chamber for varying ratesof fuel consumption is disclosed in U. S. Patent No. 1,824,952 toGraham. In this disclosure, as

in Peabody, Graham varies the quantity of fuel that oil be supplied tothe tip chamber at such a rate as to maintain an adequate whirling orcentrifugal action in the chamber.

The present invention is directed to an improved method and apparatusfor manually or automatically controlling the quantity of oil burned bya mechanical burner of this general character and at the same timemaintaining the desired burner efficiency.

As the oil firing art has developedone of the problems encountered hasbeen the difllculty of obtaining a mechanical burner having a sufficientdegree of rangeability, that is, a burner which atomizes oil at rates offlow varying from a relatively low rate to a relatively high rate, andwhich at the same time produces substantially the same kind of spray forthe different rates of flow. Several ways have been proposed for solvingthis problem. According to one system, as described in' U. S. Patent No.1,628,424 to-Peabody, oil is supplied to the burner. under pressure butnot at a constant rate of flow and a retum line is provided from theburner either to the pump intake or to the oil source. When the returnline is closed off all the oil supplied to the burner tip chamber flowsout through the d scharge nozzle of the burner and under. this conditionthe tangential passages are, supplysprayed by changing the opening of avalve in a return line and in addition provides diiferential pressurecontrol which is intendedto maintain a constant pressure differencebetween the burner input line and the return line. Thus, as the staticpressure in the burner tip chamber is reduced by opening the valve inthe return line the supply pressure is reduced an equal amount whichtends to maintain constant the amount of fuel supplied the burner tipchamber.

Inasmuch as this system employs a variable restriction in the returnline to effect variations in the rate of fuel consumption it has thesame disadvantages when used in connection with automatic control asthose described above inconnection with the Peabody system.

In any type of mechanical atomizingburner using a return flow thequantity being sprayed is the difference between the rate of oil .flowto 1 the burner and the rate of oil flow returned from Therefore, anyquantity change in return flow-will appear as a magnified percentagechange in the fuel discharge rate. Thus, it is cause it provides for thedesired correlation of the fuelconsumption with the demands of a controlinstrument which in turn is responsive to the behavior of the controlledtemperature. Further, the present invention provides for the removal ofone or more burners, for cleaning or repair, from a plurality of burnersconnected in parallel without disturbing the total fuel consumption atthe time the burners are removed.

In the accompanying drawings,

Figure 1 shows a diagrammatic layout of a system embodying theinvention; and

Figure 2 shows diagrammatically the crosssection of a mechanical burnerof the type described; and v Figure 3 is a section taken along. the line3-3 of Figure 2. I g V Referring to Figure l, the numeral I. indicatesthe combustion space of a furnace 2, which may be equipped with aplurality of mechanical atomizing burners 3 connected in parallel andwhich may be of the type shown diagrammatically in Figure 2.

Referring to Figure 2, the burner 3 includes an inner cylindricalconduit and an outer concentric conduit 16. Oil flowing to the burnerpasses through an inlet connection I1 and the annular space between theconduits I5 and 16 to the burner tip I8. At the burner tip the oil flowsthrough a plurality of small passages or jets I9 to a cylindrical burnertip chamber 80. The axes of the passages 19 are approximate y tangent tothe cylindrical inner surface of the chamber 80 so that the oil is givena rapid whirling motion as it enters this chamber. A portion of thewhirling mass of oil in the chamber 80 flows out of the dischargeorifice BI and is atomized to form a fine conical spray whereas theremainder of the oil passes through a passage 82 to the inner conduit I5and thence through the burner outlet or return connection 83. The rateat which oil is discharged through'the orifice 8| may for practicalpurposes be considered as depending upon the static pressure in the chamber 80.

Referring again to Figure 1, suitable ducts 4 may be provided to admitair to the combustion space I. A constant volume pump 5, such as a motordriven gear pump, is connected by a line 6 to the burners and serves tosupply oil to the burners. Since for the reasons pointed out above it isdesirable to supply oil through the tangential jets of the burners at aconstant rate regardless of the burner output, a constant volume pump ispreferably used to pump the oil to the burners. However, since it mayoften be impractical to select a constantvolume pump of the exactcapacity or one with an adjustable speed to supply the oil to the burnerat the rate desired, provision is made by the present invention for useof a constant volume pump of larger capacity than that required and aby-pass 5a having a manually operable Valve 5b is connected across theoutput line 6 and the suction side of the pump. As will be described,the net output of the pump to the burners may be adjusted jets IQ of theburner.

by adjusting the valve 5b and for each adjustment the rate of gil flowthrough the tangential jets remains substantially constant regardless ofthe output of the burners.

That portion of the oil supplied to the burners which is not dischargedinto the combustion space I passes without restriction through thereturn line I. to the suction of the pump 5. Thus, the

lines 6 and 1, the pump 5, and the burners 3 form a. closed circulatingsystem.

Each of the burners 3 is provided with a bypass line 3a containing arestriction 3b. The

restriction 3b is constructed in such a manner as to have the same flowcapacity and preferably the same flow characteristic as the tangentialnecessary to take one of the burners out of service to clean it or forother purposes and in such a case valve 3d in branch line 3e and valve 3in branch line 3g are closed and valve 30 in by-pass line 3a is opened.Due to the presence of the restriction 3b in the by-pass line 3a thesame quantity of oil will flow throughthe branch lines 3g when theburner is not in service as when the burner is in service. A furtheradvantage resulting from the use of the bypass 3a is that since a flowof oil through the branch lines is maintained when the burner is out ofservice, the viscous oil frequently used as a fuel will not cool andcongeal in the branch lines. For the same reason the by-pass 3a=shouldbe short and located in the block'of the burner so that it will stayhot. Although the output of the burners remaining in service increases,the quantity of oil flowing to the burner tip chambers of the burner orburners which remain in operation will be maintained constant and hencethe spray characteristic of the remaining burners and their efficiencieswill be the same as before. As the description proceeds it will becomeapparent that the burner or burners left in service will automaticallyassume the load normally carried by the burner taken out of service, andthe quantity of oil discharged into the combustion space I will alsoremain constant.

Referring to the lower left-hand corner of Figure 1, there is shownanoil storage tank 8 from which oil to make up the oil discharged fromthe burner nozzle flows to the circulating system through a pipe 9 underthe pressure supplied by a suitable positive displacement pump I 0 inthe line 9 between the tank 8 and the pump 5. When the fuel being burnedis a heavy residual fuel oil suitable heating means may be provided atvarious points in the system to maintain the fuel in a desirably fluidcondition.

Since oil is a non-compressible fluid and the circulating system iscompletely filled with oil,

the rate at which oil is discharged into the combustion space I by theburners 3 is precisely equal to the rate of flow of oil in line 9, andin accordance with the'present invention the flow of oil in the line 9is metered and controlled to control the discharge of the oil from theburners. This metering and control of the oil flow in the line 9 isaccomplished by a flow controller, generally indicated at I3, whichincludes an orifice I4 in the 'line 9. The operating means of the flowcontroller is a pneumatic pressure which operates a valve I2 in a liquidreturn line II.

The valve I2 serves as a variable restriction in the line II to vary theflow in the line 9. The flow controller thus acts in response to thepressure difference across the orifice l4 to maintain the flow throughthe line 9 at a desired value Occasionally it becomes heaters; as itmoves to the right the pressure in lines 49 which may be considered asthe control point of the flow controller.

This desired value or control point may itself be varied or set up ordown by a temperature controller, generally indicated at 29. Thetemperature controller is responsive to a temperature sensitive element90 in thefurnace 2 and the operating means of the temperature controlleris a pneumatic pressure the value of which determines the setting of thecontrol point or the flow controller I3. Thus, with this system anaccurate correlation between the behavior of the temperature of thefurnace 2 and the oil burner is obtained.

The orifice meter shown is essentially a U- .tube comprising a highpressure leg I5, a low.

and 50 decreases.. The operation of the valve 48 is such that as theflapper 49 'and nozzle 4| approach one another, pressure tends to buildwhereas as the flapper 49 and nozzle 4| recede from one another pressurein line 45 tends to decrease, contracting bellows 5| to move plunger 41to the left, as shown, thus increasing pressure in lines 49 and 59.

Nozzle 4| is positioned by link 59 which is in 7 turn positioned by acompound lever 56 and in pressure leg I6. and a pipe l1 connecting thetwo. The meter is partially filled with mercury,

the level of the mercury in the high pressure downstream of the orificel4 through'aline 22.

Suitable se'als (not shown) may be used when necessary to prevent thefuel flowing in the line 9 from entering the. meter piping or chambers.

Floating on the surface |5a of the mercury in high pressure leg I5,there is a float 28 provided the arrangement shown link 59 is positionedthrough compound lever 59 by either or both of the bellows 59 and 91acting through links 55 and 99, respectively. The bellows 53 and 61 arerigidly secured at one end and at their other end move against-theaction of springs 54 and 98 to move links 55 and 99 which are pivotallyconnected to the compound lever 55 at the lower end 58 and upper end 51of the lever 55.

The line 59 communicates with the interior of the bellows 53, andif-tl1e pressure in bellows 61 is maintained at a constant value changesin pressure in line 50 will produce corresponding with a vertical mast29 connected by a chain 39 to an arcuate member 3|. The arcuate member3| is mounted on a lever arm 32 which is secured to and supported by arotatable shaft 33 mounted in a suitable bearing 34 located in thewallof the high pressure leg 15. The shaft 33 carries a, lever arm 35located outside of the high pressure leg IS. The construction is suchthat if, for example, the difierential across the orifice plate l4increases, mercury flows from the high pressure leg into the lowpressure leg to balance vary the pressure on the valve 2 and so positionit in the following manner. At its lower end 'the lever 35 is connectedby a link 36 to flapper 40, and thus the flapper is positioned inaccordance withthe difierentialpressure across the orifice plate Hi. Theposition of the flapper is translated into a proportional pneumaticpressure for operating valve l2 by follow-up mechanism that will now bedescribed.

Cooperating with the flapper is a movable nozzle 4|. A portion of theair from a supply line 42 passes through abranch line 43, a restriction44, and branch line 45 to the nozzle 4| and to a bellows 5| operating avalve plunger 41 of a double-seated valve 49. The'double-seated valveregulates the pressure in a line 49 connected to the control valve l2and in a line 50 connected with a bellows 53 which forms a part of thefollow-up mechanism. The operation of the double-seated valve is suchthat as the plunger 41 moves to the left, as shown in the drawings, thepressurein lines 49 and 59 increases and changes in the position of thenozzle 4|. Since a static balanced pressure condition would require theplunger 41 to be in some mid-position between its two seats, thefollow-up mechanical arrangement will require the nozzle to be sub:-stantially tangent to the flapper, and since the pressure in' lines 49and 5|) also governs the opensure in the bellows 51 or the position ofthe pivot 51. If the pressure in bellows 61 is increased the initialoperation is to move nozzle 4| clockwise a proportionate amount, thusseparating nozzle 4| from flapper 40. This initial operation causes thepressure in lines 49 and 59 and in bellows 53 to increase which willretard or reverse the clockwise movement of nozzle 4| and at the sametime increase the flow through the orifice plate M. The increaseddiiferential pressure across orifice M will rotate flapper 40 in aclockwise direction and a new static pressure and static flow conditionwill be established such that the increase in flow is proportional tothe increase in pressure in bellows 61. If the pressure in bellows 61 isdecreased the operation of the parts is reversed and flow in the line 9is decreased in proportion to the decrease in pressure in bellows B1.

In the present embodiment a pneumatically operated temperaturecontroller is used to reset the control point of the flow controller I3in the manner described above and hence control the amount of oilsprayed by the burners 3 in response to variations in the temperature ofthe .furnace 2.

The temperature controller 20 will now be described more in detail.

The temperature sensitive element 60 in the with the value of themeasured temperature. The position of the flapper 84 is translated intoa pneumatic pressure in the line 6 6 in a manner similar to thatdescribed in connection with the flow controller l3.

Cooperating with the flapper 64 there is a variable nozzle 65, A portionof the supply air passes through a .restriction I4 to the nozzle 65 andto a bellows 13 operating the plunger of a double-seated valve 12. Thedouble-seated valve 12 regulates the pressure in line-58 and a bellows10 which, like bellows 53, operates to maintain the nozzle substantiallytangent to the flapper flapper 64 rotates in a clockwise direction, thusincreasing the pressure in bellows 13, reducing the pressure in line andin bellows 10 to cause the nozzle to follow the flapper. This reductionin pressure is transmitted through line H to bellows 61 and theresulting initial counterclockwise movement of nozzle 4 increases thepressure in bellows to cause the double-seated valve 46 to decrease thepressure in bellows 53 to hold the nozzle 4| tangent to the flapper 40.The resulting decreasing pressure in line 49 opens valve l2 anddecreases the flow through orifice l4 until the change in flow in line9, and thus in the amount sprayed'by the burners, is proportional to thechange in pressure in bellows Bl. The resulting proportionate fuelreduction tends to prevent further increase of the measuredtemperature,and the action continues until a new static temperature, new operatingair pressures. and a new flow balance are reached. If the load on thefurnace 2 increases so that the present amount of fuel being burned bythe burners causes the temperature of the furnace todrop, by similar andopposite reactions the flow of fuel is increased until a new statictemperature, new operating air pressures, and a new flow balance arereached.

v Thus, the flow of fuel is positively correlated with the operatingmeans of the temperature controller. It should be understood that thecontrol characteristics of the temperature controller 20 as well as ofthe flow controller I3 may be changed from that shown in the drawings byadding other instrumentalities to overcome lag complications in theprocess being controlled.

It is apparent that in order to maintain a uniform spray characteristicwith varying quantities of fuel sprayed it is necessary to maintain auniform flow through the tangential jets of each burner. Since in thesystem embodying the present invention there are no appreciablerestrictions in the return line under any condition of flow in thereturn line the pressure on the suction of the pump 5 is substantiallyequal to the static pressure in the burner tip chamber. Therefore, thepressure drop acrossthe by-pass valve 512 is substantially equal to thepressure drop across the tangential jets of the burner. Furthermore, thepressure drop across the tan gential jets and across the by-pass valve512 is constant for all rates of flow of make-up oil and hence for allburner discharge rates. The reason for this is that the pump 5 is aconstant volume pump which is operating on a non-compressible fluid andso the sum of the flows through the by-pass line and the tangential jetsis equal to the pump output and is constant. Further, since the pressuredrops across the by-pass valve and the tangential jets are always equal,the ratio of the flow through the by-pass line to the how through thetangential jets is constant. Therefore, the rate of flow through thetangential jets is constant and is unaflfected by variations in the rateof flow of make-up oil.

4 Since many embodiments might be made in the above invention, and sincemany changes might be made in the embodiment above described, it is tobe understood that all matter hereinbefore set forth or shown in theaccompanying drawings is to be interpreted as illustrative only and notin a limiting sense.

We claim:

1. The method of regulating the temperature of a furnace fired by an oilburner of the oil recirculating type utilizing mechanical means toatomize the oil burned, which comprises establishing a constant volumeflow from a pump to said burner at a rate in excess of the rate at whichoil is atomized for burning by said burner, recirculating excess oil notatomized back to said pump in a closed circulating system, supplyingmake-up oil from a source of oil to said circulating system andcontrolling the rate of flow of make-up oil to said system at a pointintermediate said source and said circulating system and in response toa variable condition influenced by the temperature in said furnace.

2. Method of regulating the temperature of a furnace fired by an oilburner of the oil recirculating type utilizing mechanical means toatomize the oil burned, which comprises pumping oil into said burner ata constant volume rate in excess of the rate at which oil is atomizedfor burning bysaid burner, recirculating excess oil not atomized back tosaid pump in a closed circulating system, supplying make-up oil to thelow pressure side of said circulating system, metering the flow of saidmake-up oil and using a variable condition influenced by temperaturevariations of saidfurnace to vary the metered flow to maintain saidtemperature at a substantially constant value.

3. Method 'of controlling the oil sprayed by a mechanical atomizingburner of. the oil recirculating type, which comprises establishing aconstant volume flow from a pump to the burner, returning anunrestricted flow of excess oil not sprayed back to the pump, supplyingmake-up oil to said pump, measuring the quantity of the make-up oil thussupplied, and controlling the amount of oil sprayed by-regulating theamount of make-up oil in response to variations in the measured quantityof make-up oil.

4. Method of controlling the burning characteristics of the oil flame ofa mechanical atomizing burner of the oil recirculating type, whichcomprises establishing a constant volume flow of oil to the burner inexcess of the quantity of oil burned, recirculating excess oil notburned to establish a closed system, supplying make-up oil to the saidsystem, measuring the rate at which make-up oil is supplied to saidsystem, and controlling the amount of oil burned by controlling themake-up oil supplied in response to variations in the measured rate offlow of make-up oil.

5. Apparatus for controlling at a control point a condition of a furnacefired by an oil burner of the oil recirculating type utilizingmechanical means for atomizing the oil burned, comprising, incombination with said burner, an oil circulating system including aconstant volume pump for supplying oil to said burner at a constantvolume rate in excess of the rate at which oilis atomized by saidburner, and means for recirculating excess oil to said pump, meansincluding a conduit for supplying make-up oil to said system, a flowcontroller associated with said conduit for controlling the rate of flowof makeup oil supplied through said conduit to said cirof a furnacefired by oil burners utilizing mechanical means to atomize th oil burnedand uring the quantity of make up oil supplied, and

culating system, and means for regulating said i flow controller inresponse to the said condition of said furnace.

6. The method of regulating the temperature of a furnace fired by an oilburner of the oil said burner at a rate in excess of the rate at' whichoil is atomized for burning by said burner, recirculating excess oil notatomized back to said pump through an unrestricted passage to form aclosed circulating system, supplying make-up oil from a sourceof oil tosaid circulating system, and controlling the rate at which make-up oilis supplied to said system at a point intermediate said source and saidcirculating system and in response to a variable condition influenced bythe temperature in said furnace.

7. A method for controlling the burner output of a plurality ofmechanically atomizing oil burners of the oil recirculating typeconnected in parallel to the discharge of a pump, each burner being alsoconnected through an unrestricted return line with the intake of thesaid pump to return excess oil not burned and each burner having apredetermined resistance coeificient to the flow of oil therethrough,comprismg pumping a constant volume of oil. to said burners regardlessof the burner output, retur n ing all not burned through saidunnrestricted return line, supplying oil to the intake side 01 said pumpto make up the oil burned, and insertmgin the return line of a burnertaken out of service a restriction having substantially the same flowcoeflicient as the burner removed whereby the volume of oil pumped toeach burner remaining in service remains the same, and the flamecharacteristic of the burners remaining in service remains substantiallythe same.

8. Apparatus for regulating the temperature of a furnace fired by an oilburner otthe oil recirculating type using mechanical means to atomizethe oil burned, comprising, in combination, a closed oil circulatingsystem including one or more burners, a constant volume pump providedwith a by-pass containing a variable restriction, an oil supply line forsupplying oil to said burners from said pump, and an oil recirculatingline providing an unrestricted passage for now of oil from said burnersto said pump, a source of oil,

means for supplying make-up oil from said source to said system, andmeans responsive to the temperature or said furnace for controlling at apoint intermediate said source of oil and said circulating system therate at which makeup oil is supplied to control the rate at which oil isatomized by said burner.

9. Apparatus for regulating the temperature means responsive to thetemperature of said furnace' and to the measured quantity of make-up oilfor controlling the rate at which make up oil is supplied to control therate at which oil is atomized by said burners.

10. In apparatus for controlling the quantity of oil burned by oilburners utilizing mechanical means to atomize the oil burned and whereinfor efllcient atomization oil is supplied to said burnrs at a constantvolume rate in excess of the rate at which oil is atomized by saidburners, in combination, a, supply line and means for supplying oil tosaid line at a constant volume rate, a plurality or burners connected inparallel to said line and each provided with a plurality of tangentialjets providing restriction to flow of oil therethrough, and means forcutting out one of said burners from service without changing the totalrestriction to oil flow through the system,

' said means including an oil by-pass -line around each of said burnerscontaining a predetermined fixed restriction having the same flowcapacity as the tangential Jets of said burner to permit continual flowpast said out out burner through a fluid path having the same flowresistance as the jets of said burner, whereby the volume rate of oilnow to each of the remaining burners remains unchanged.

11. In apparatus. for controlling the quantity.

of oil burned by oil burners utilizing mechanical means to atomize theoil burned and wherein for efllcient atomization oil is supplied to saidburners at a constant volume rate in excess of the rate at which oil isatomized by said burners, in combination, a closed oil circulatingsystem in-.-

cluding a constant volume pump for circulating oil in said system, anoil supply line for supplying oil to said burners, a plurality ofburners cutting out one of said burners from service including an oilby-pass line around each of said burners containing a predeterminedfixed restriction having the same flow capacity as the tangential jetsoi said burner to permit continual flow past said out out burnerthroughv a fluid path having the same flow resistance characteristics asthe jets of said burner, whereby the volume rate of oil flow to each orthe remaining burners remains unchanged.

CLESSON E. MASON.

, RALPH A. ROCKWELL.

